colorspaceSpot colors, mixed inks and moreVersion 1.2.0 (2016-10-05)

Javier Bezos (http://www.texnia.com)

The aim of this package is, as its name implies, to provide tools for PDF color spaces. Itrequires xcolor, which is loaded if it has not been before. It seems to work with tikz.

Currently it supports what I think are the most common tools:

• Spot colors, with a clean user interface, and including tints (with the ! notation).

• CIE LAB spot colors.

• Proper switching of color spaces.

• Mixed spot and process colors (up to 4), like shades (ie, a spot color with black).Also CIE LAB if a CMYK equivalent is provided.

• ICC based (or “tagged”) default CMYK, RGB and Gray spaces.

• Overprinting (across pages, using the color stack).

Currently only pdftex and luatex are supported. Support for xetex is on the ‘to do’ list,but due to the limitations of this engine this task is somewhat challenging and I’m notsure all features will be implemented.

Other functions related to the PDF color spaces (indexed, calibrated, Lab spaces) arenot yet suported, but they are under study. Calibrated colors, although not directlysupported, can be defined with an ICC profile created with LPROF1 and then assignedto a default space as described below.

They apply to text and line art only, not external images. For the latter, graphicxprovides a plea of (undocumented) transformations: interpolate, decodearray,maskarray, intent, ocobjnum, and ocobjref. For transparency, see transparent, byHeiko Oberdiek.

This package is still evolving, but the basic behaviour described here will be preservedin future versions. However, some functions from xcolor might not work yet (forexample \selectcolormodel).

Declarations are global and should go in the preamble.

This package is built on the previous attempts to provide spot colors and otheradditional features by Jens Elstner, Stephan Lehmke and Siep Kroonenberg (with someinspiration from ConTeXt, too).

1 CMYK spot colors

Spot colors are defined with a single macro:

\definespotcolor{〈latex-name〉}{〈PDF-name〉}{〈CMYK-equivalent〉}

Here 〈latex-name〉 is the LATEX name, as used in \color and the like, 〈PDF-name〉 is thePDF name (usually taken from a swatch book; multiple spaces are collapsed into one)

1http://lprof.sourceforge.net/

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as shown by PDF viewers, and the four numbers are the CMYK equivalent. LATEX knowsnothing about the PDF name, which is just a string to be written to the generated file,while the PDF knows nothing about the LATEX name.

To mix inks, see below.

EXAMPLE Write, for example:

\definespotcolor{foo}{BarTone 555 GN}{.8,.2,.5,.3}

This creates the color , which is used in LATEX as \color{foo}. If youpreflight the PDF file you will see a color named ‘BarTone 555 GN’ besides cyan,magenta, yellow and black.

You can use tints as usual in xcolor, like:

\color{foo!50}\colorlet{foo50}{foo!50}

which would produce , and even set tints from other tints.

NOTE The special PDF names All (for all plates) and None work as expected:

\definespotcolor{registration}{All}{1,1,1,1}

NOTE Remember as far PDF is concerned a spot color is a color space on its own.

NOTE This package does not provide a list of Pantone, TrueMatch, HKS, Folcoltone,Toyo, etc., colors. Currently you can find quite easily CMYK equivalents on theweb, and after all they are intended to be used with a “physical” swatch book (andnot, as often done, by picking a color from a “virtual” palette just because it looksnice on screen).

\definespotcolor{〈latex-name〉}{〈PDF-name〉}[〈model〉]{〈equivalent〉}

Internally, only CMYK is used for the equivalent color, but with this variant you candefine the latter with another name space, which is then converted.

EXAMPLE The following definition is based on RGB:

\definespotcolor{foob}{BarTone 666 GN}[rgb]{.8, .2, .4}

which yields . Here xcolor just converts this value to CMYK, which is still thespace used internally.

WARNING This conversion relies on the xcolor numerical methods, which do not takeinto account any color profile and therefore should be avoided in production if thealternate space is going to be actually used. It is provided just for convenience indrafting or in contexts where accuracy is not essential.

2 CIE LAB spot colors

Instead of targeting the CMYK space, spot colors may be defined using the CIE LAB(also known as L*a*b*, or even just Lab) space. Unlike the default CMYK space, whichis by default device dependend, the Lab space is device independent. To define a Labspot color, you must first set the illuminant with the package option illuminant, whichtakes a value:

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\usepackage[illuminant=d65]{colorspace}

Values are a, c, e, d50, d55, d65, d75.

The command to define a color is:

\definespotcolor{〈latex-name〉}{〈PDF-name〉}[alt=lab]{〈Lab-values〉}

Note the optional argument with the string alt=lab (which cannot be combined with amodel). The three 〈Lab-values〉 have ranges L* = 0. . . 100, a* = −128. . .127, b* =

−128. . . 127, respectively.

EXAMPLE With

\definespotcolor{foolab}{BarTone 888 LB}[alt=lab]{50, -30, -40}

the result is . An example of tint is \color{foolab!30} ( ).

WARNING The package does not warn if the color falls outside the gamut of the CMYKspace or if the color is not visible. To put it in other words, you should not justwrite some arbitrary values to see what happens.

WARNING This model is not available in xcolor. If you need some transformation, youmust resort to an external tool like transicc (or icctrans) included in Little CMS2.

WARNING There is no default illuminant – it must be set if Lab colors are defined.

NOTE The observer is currently only 2◦ (1931).

The Lab space allows to define colors accurately, but there is a price to pay – mixingLab colors is not in general possible except after converting them somehow to CMYK orRGB.3. Since currently mixing colors in this package is based on CMYK, you mustprovide an alternate value as shown, if mixed inks are required4:

\definespotcolor{foolab}{BarTone 888 LB}[alt=lab]{50, -30, -40/1, .20, .15, .07}

3 Mixing spot colors

To mix spot colors you must first declare a color space (or model) including them. Thisis done with the following macro:

\definecolorspace{〈latex-name〉}{mixed}{〈color-list〉}

Here, 〈latex-name〉 is the name to be used in \color and the like as the color model.The second argument is the string mixed, and the last one is a list of up to 4 colors,either defined with xcolor using the CMYK model or spot.

EXAMPLE A simple and typical usage would be for shades:

\definecolorspace{fooshaded}{mixed}{foo,black}

2http://www.littlecms.com/1/downloads.htm3There are no simple rules to carry out those transformations, which, I think, explains why xcolor does not

support Lab at all4Internally, and in PDF jargon, Lab is the “alternate space” and “tints transforms” are based on CMYK

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Then, you can define a color in this new model named fooshaded with:

\definecolor{darkfoo}{fooshaded}{.6,.3}

Or set it with:

\color[fooshaded]{.6,.3}

In both cases, the mix is 60% foo and 30% black.

EXAMPLE If we have two spot colors named spot1 and spot2, and we want in additionyellow:

\definecolorspace{mix12y}{mixed}{spot1,spot2,yellow}

To define a new color based on this space:

\definecolor{mix12y}{mix12y}{.5,.4,.6}

And to set it:

\color[mix12y]{.5,.4,.6}

EXAMPLE Here is a duotone mixing the foob and foolab colors defined above:

\definecolorspace{labshaded}{mixed}{foolab,foob}

The colors corresponding to:

\color[labshaded]{1,0} \color[labshaded]{.8,.2}\color[labshaded]{.6,.4} \color[labshaded]{.4,.6}\color[labshaded]{.2,.8} \color[labshaded]{0,1}

are

WARNING Due to internal limitations of xcolor, no more than four colors are allowed.

NOTE The alternate color space in the PDF file is that of the spot colors (which meanscurrently it is CMYK).

NOTE There is an easy trick to mix colors with ! and color,num – just define anortogonal set of colors based on the new color model:

\definecolor{xspot1}{mix12y}{1,0,0}\definecolor{xspot2}{mix12y}{0,1,0}\definecolor{xyellow}{mix12y}{0,0,1}

and then you can say:

\color{xspot1!30!xspot2!40!xyellow}\color{mix12y:xspot1,3;xspot2,2;xyellow,1}

Of course, it is just a trick and a better and direct interface is under study (noneof those provided by xcolor fits well with the new mixed models).

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Figure 1: Plate for the foo spot color as shown by Adobe Acrobat. Note both foob andfoolab, defined in this document, are listed, too.

WARNING Mixing colors in \color, \definecolor and the like from diferent spacescan lead to unexpected results (currently no checking is done).

Color series (see the xcolor documentation) are also partially supported. For example:

\definecolorseries{test}{mix12y}{grad}[mix12y]{.95,.85,.55}{3,11,17}\definecolorseries{test}{mix12y}{last}{xyellow!50}{xspotA}

EXAMPLE Here is a example with some of the described techniques, based on thefooshaded space defined above (figure 1 shows the foo plate):

\definecolor{sfoo}{fooshaded}{1,0}\definecolor{sblack}{fooshaded}{0,1}\definecolorseries{shseries}{fooshaded}{last}{sfoo!40}{sblack}\def\testclr#1{{\fboxsep0pt\fbox{\colorbox{#1}{\phantom{XX}}}}}\resetcolorseries[8]{shseries}\begin{tabular}{cccccccc}

0 \testclr{shseries!!+} &1 \testclr{shseries!!+} &2 \testclr{shseries!!+} &3 \testclr{shseries!!+} &4 \testclr{shseries!!+} &5 \testclr{shseries!!+} &6 \testclr{shseries!!+} &7 \testclr{shseries!!+}

\end{tabular}

0 1 2 3 4 5 6 7

4 Page color spaces

Each PDF page must know which colors will be used (other than the predefined CMYK,RGB and Gray). By default, colorspace turns on for every page all newly defined colors,

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and that will be fine in most cases. However, you may want to set explicitly the list (forcovers or plates). Use this feature with care, because (1) the asynchronous nature ofTEX (remember it affects the whole current page), and (2) each distinct color listcreates a PDF resource.

\pagecolorspace{〈color-list〉}\resetpagecolorspace

To change the color space for a page and the subsequent ones, you can set somethinglike:

\pagecolorspace{name1,name2,name3}

(It can be empty.) To return to the default color space, which contains all the definedspot colors, use \resetpagecolorspace.

5 ICC based spaces

\definecolorspace*{〈latex-name〉}{iccbased}{〈icc-file〉}

The starred version \definecolorspace* does not define a new color model, but setsthe behaviour of the three basic color spaces (CMYK, RGB and Gray). When belongingto the same space, the last definition for that space takes precedence and it isconsidered the default one. It cannot be used to define new colors or set them.Currently, only a type is supported – iccbased. For example,

\definecolorspace*{sRGB}{iccbased}{sRGB Profile.icc}

The space it applies to is read from the ICC profile.

The name can be used in \pagecolorspace. Alternatively, there are 3 reserved names:

*rgb, *gray, *cmyk, which stand for the last-defined, default ICC based spaces. NamedICC based spaces are not set by \resetpagecolorspace, but the starred named are. Onthe other hand, the starred names are not set automatically by \pagecolorspace, andyou must set them explicitly if you want them to be active.

NOTE Those ICC spaces do not go to the output intent dictionary (see the pdfxpackage). The latter, as the PDF reference explains, supplements rather thanreplaces the ICC profiles in a default color space.

EXAMPLE Given the following declarations:

\definecolorspace*{sRGB}{iccbased}{sRGB Profile.icc}\definecolorspace*{colormatch}{ColorMatchRGB.icc}

and remembering the RGB space is always active (like the CMYK and Gray ones),

\pagecolorspace{}

leaves the RGB space unprofiled;

\pagecolorspace{sRGB}

sets the RGB space to sRGB; while the following are (in this particular example)equivalent:

\pagecolorspace{colormatch}\pagecolorspace{*rgb}\resetpagecolorspace

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6 Overprinting

This is usually a pre-print task, but by setting it in the document you will get a betteridea of how the colors are actually overlapped in soft proofing. However, remember theeffect produced is device-dependent, and colorant overprint decisions should be madeat output time (according to the PDF reference).

Very often, it is set for the whole document with the package options knockout (nooverprint), and overprint. By default, the overprint mode is 1, but it can be changedwith opm=0.

Once set the overprint state for the whole document, you can use something like:

{\overprintstate{1}text}\textoverprint[1]{text}

(or 0, or no; default in \textoverprint is 1, except with the package option opm=0).

Since the color stack is used, pdfTEX ≥ 1.40 is required.

WARNING Some PDF viewers ignore this setting.

7 Version

1.1.1. No new features. Just internal changes related to luatex and new manual.

1.2.0. CIE LAB spot colors and illuminant. Manual rewritten.

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